1. Technical Field
The present invention relates to an ejection liquid dryness suppressing device, a liquid ejecting apparatus, and an ejection liquid dryness suppressing method.
2. Related Art
There is known a liquid ejecting apparatus that forms a predetermined image (including characters, figures, and the like) by allowing a liquid ejecting unit (for example, a printing head) to eject an ejection liquid (for example, ink) toward a medium (for example, a sheet). Such a liquid ejecting apparatus includes an ejection liquid dryness suppressing device capable of suppressing drying of the ejection liquid in the liquid ejecting unit so as to stably eject from the liquid ejecting unit. The ejection liquid dryness suppressing device can be equipped in the liquid ejecting unit to suppress the drying of the ejection liquid by bringing a contact member into contact with a nozzle formation surface in which nozzle openings are formed, which are the end openings of the nozzles ejecting the ejection liquid, and covering the nozzle openings with the contact member, when no image is being formed. The contact member brought into contact with the nozzle formation surface is separated from the nozzle formation surface in the ejection liquid dryness suppressing device so that the ejection liquid is ejected from the nozzle openings, when an image is being formed.
As such a kind of device, there is known a device (capping device) configured to cover the nozzle formation surface by allowing the cap-shaped contact member to form a closed space between the cap-shaped contact member and the nozzle formation surface. In such a device, there is a little concern that a meniscus (interface between the ejection liquid and the atmosphere) formed in the nozzle is broken down due to the contact member, since the contact member does not come into direct contact with the nozzle openings. However, there is a concern that a solvent component evaporating until the pressure of the closed space reaches a saturated vapor pressure and thus the ejection liquid dries out.
In order to suppress the drying of the ejection liquid, there have been suggested various techniques capable of stably forming the meniscus by bringing the contact member into direct contact with the nozzle formation surface without a space, that is, by closely contacting the contact member with the nozzle formation surface and covering the nozzle openings with the contact member (for example, JP-A-2002-292885 and JP-A-2009-029113).
However, in the devices disclosed in JP-A-2002-292885 and JP-A-2009-029113, it is actually difficult to allow nozzle formation surface or the contact surface of the contact member to be completely flat. Accordingly, since it is considerably difficult to simultaneously open all of the blocked nozzle openings, there are nozzles in which the nozzle openings are not opened and the nozzles in which the nozzle openings have already been opened in the blocked nozzle openings.
However, for example, in the contact state of the contact member, the ink exudes from the nozzle openings, in which the ink is contacted with the contact surface, due to capillarity occurring between the contact surface and the nozzle formation surface at the moment when the contact surface is separated from the nozzle formation surface. In this case, the amount of exuded ink is supplied and supplemented from the common liquid chamber (reservoir) communicating with each nozzle.
At this time, when there are the nozzles in which the nozzle openings have not yet been opened and the nozzles in which the nozzle openings have already been opened, the supplementary ink is supplied from the nozzles in which the nozzle openings have already been opened. That is, since the atmosphere (air) can intrude into the opened nozzle opening in the nozzle in which the nozzle opening is opened, the ink in the nozzle can flow toward the common liquid chamber from the nozzle opening. Therefore, since the ink is supplemented to the nozzle, in which the nozzle opening has not yet been opened, from the nozzle, in which the nozzle opening has already been opened, via the common liquid chamber, the ink in the nozzle in which the nozzle opening has already been opened may be decreased.
In the nozzle in which the ink is decreased, the meniscus in the nozzle is drawn inward and thus the position of the formed meniscus may be changed. As a consequence, the meniscus is moved and formed at a position different from the position at which the meniscus is to be formed when an image is formed. Therefore, a problem may arise in that the amount of ejection liquid may not be correctly ejected from the nozzle openings to form the image, and thus, for example, dot omission occurs.